Title: Isoleucine
CAS Registry Number: 73-32-5
CAS Name: L-Isoleucine
Additional Names: Ile; I; 2-amino-3-methylvaleric acid; a-amino-b-methylvaleric acid; (2S,3S)-2-amino-3-methylpentanoic acid
Molecular Formula: C6H13NO2
Molecular Weight: 131.17
Percent Composition: C 54.94%, H 9.99%, N 10.68%, O 24.39%
Literature References: An essential amino acid for human development. Isoln from beet-sugar mother liquors: F. Ehrlich, Ber. 37, 1809 (1904). Structure and identification of isomers: idem, Ber. 40, 2538 (1907); J. P. Greenstein et al., J. Biol. Chem. 204, 307 (1953). Early chemistry and biochemistry: Amino Acids and Proteins, D. M. Greenberg, Ed. (Charles C. Thomas, Springfield, IL, 1951) 950 pp., passim; J. P. Greenstein, M. Winitz, Chemistry of the Amino Acids vol 1-3 (John Wiley and Sons, Inc., New York, 1961) pp. 2043-2074, passim. TLC determ in serum from patients with maple sugar urine disease (MSDU): R. J. Allen et al., Clin. Chem. 18, 413 (1972). Metabolism of Ile and isomers in MSDU: U. Wendel et al., Pediatr. Res. 25, 11 (1989); and clinical consequences: T. Mogos et al., Rev. Roum. Med. Interne 32, 57 (1994). Review of biosynthesis: M. Iaccarino et al., Curr. Top. Cell. Regul. 14, 29-73 (1978).
Properties: Waxy, shiny, rhombic leaflets from alc. Bitter taste. Sublimes 168-170°. Dec 284°. [a]D20 +40.61° (c = 4.6 in 6.1N HCl); +11.09° (c = 3.3 in 0.33N NaOH). [M]D +53.5° (5N HCl); +64.2° (glacial acetic acid). pK1 2.36; pK2 9.68. Soly in water (g/l): 37.9 at 0°; 41.2 at 25°; 48.2 at 50°; 60.8 at 75°; 82.6 at 100°. Sparingly sol in hot alc (0.13% w/w at 80°), hot acetic acid. Insol in ether.
pKa: pK1 2.36; pK2 9.68
Optical Rotation: [a]D20 +40.61° (c = 4.6 in 6.1N HCl); +11.09° (c = 3.3 in 0.33N NaOH)
Derivative Type: DL-Form
Additional Names: (±)-erythro-2-Amino-3-methylpentanoic acid
Properties: Glistening rhombic or monoclinic plates from dil alc. Dec 292°. pK1 2.32; pK2 9.76. Soly in water (g/l): 18.3 at 0°; 22.3 at 25°; 30.3 at 50°; 46.1 at 75°; 78.0 at 100°.
pKa: pK1 2.32; pK2 9.76
Derivative Type: L-allo-Form
Additional Names: a-Ile; L(+)-alloisoleucine; (+)-threo-2-amino-3-methylpentanoic acid
Properties: Waxy leaflets. Sweet taste. Dec 280°. [a]D20 +14.0° (c = 2); +38.1° (c = 2 in 6N HCl). [M]D +53.1° (5N HCl); +55.7° (glacial acetic acid). pK1 2.27; pK2 9.62. One part dissolves in 34.2 parts water at 20°; 0.82 part dissolves in 100 parts 80% alcohol at 20°; 1.97 parts dissolve in 100 parts 80% alcohol; 0.19 part dissolves in 100 parts abs alcohol at 90°.
pKa: pK1 2.27; pK2 9.62
Optical Rotation: [a]D20 +14.0° (c = 2); +38.1° (c = 2 in 6N HCl)
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